Sheet detector



Oct. 18, 1932.

' A.' w. BARRETT SHEET DETECTOR Filed Feb. 10. 1930 2 Sheets-Sheet l NVENTOR Wxs-M Qa-WJX cam -fi-xmm VTILTNESSCS I Oct. 18, 1932. A. w. BARRETT I 1,833,471

SHEET DETECTOR Filed Feb. 10. 1930 2 Sheets-Sheet 2 2.9 2f 26 28 if /IIIIIIIIIIIIIIIIII'IIIIIIIII I'll/Ill E [/4 7/1/1111 WITNESSES I VENTOR Patented Oct. 18, 1932 UNITEDeST-ATES P ENT; OFFICE ALFRED WILLIAM BARRETT, or rrr'rsBuRem PEN sYLvA iA, ASSItGNORTO MILLER PRINTING MACHINERY ooNrANmor PI T BU GH, PENNSYLVANIA, A CQRPQRA-e TION' or PENNSYLVANIA HEET- Dn'rEc'ro Applicationfiled Februarylo, 1930. Serial No. 427,151,

My invention pertains to sheetldetectors for printing'presses, that is to say, devices for detecting the failure to feed a sheet when such occurs, and relates especially to sheet detec tors for use in cylinder printing presses at the .point where the blank sheets aretaken from the feedtable by the cylinder;

In the operation of cyl'nder printing presses, it is common to lay, either automatically or by handfeach sheet upon a feedtable,

. with its leading edge abutting against a pair of front guid'es, whereby the sheet is reg1 s f tered e-ndwise. The cylinder grippers seize the sheet from the feed table during the rotation of the cylinder, thefront guides being raised at theproper instant, to allow the sheet to be drawn off thefeed'table by the cylinder. Should a sheet not have'been fed to the front guides at the time the cylinder grippers close totake a sheet, a printing impression would be made on the cylinder, which impression would be reproduced,by offset, upon the backs of a number of followingsheets, when fed to the press. I To meetthissituation, various automatic mechanisms have beenput in use, designed to throw off the'impression of the press whenever failure occurred in the feed of a sheet, but difliculty has'been experienced in attaining the requisite degree of delicacy of working, and'in rendering the device sufliciently certain in its operation when, sheets having curled or upturned edges, torn edges, or the like, are encountered.

It is the principal object of myinvention to provide asheet detector which will work withexceptional delicacy, and which will opcrate with entire certainty in spite of the fact that the sheets being fed to the press maypresent obstacles to easyhandling, such as haying curledleading edges, or the like. 1 l 'j I i A sheet detector constructed inaccordance with my invention is described by way of ex ample in the following specification, and

. shown in the accompanying drawings, in

which: I p v n Fig. 1. is a plan showing a portion of a frame, feed tahle, and one of the front guides ofaa cylinder printing, press, the front guide having asheet detectingmeniber constructed in accordance with my invention applied thereto;-' 1

Fig. 2 is a side elevation of the same, the

press frame being omitted and the impression cylinder shown in section Fig. 3 is an enlarged plan of one of the front guides Fig. 4is an end view of the'same; and Fig. 5'is a vertical section taken through the front guide an'dthe feed table tongue with which it cooperates.- i

The press indicated in the drawings includes aframe in whichis rotatably sup ported, in the usual manner, a cylinder 11, and with which is associated a feed table '12 upon which the blanksheets are fed, either by hand'orautomatically, into a position in which theyare correctly placed for being drawn awayby grippers on the cylinder 1L At the front end of the feed table,is a lip plate 13, the leading edge of, which. comes close to the cylinder 'jendbeneath thefeed table is mounted a guide bar 14 upon which are supported apair oftongues 15 of which only one is shown, these tongues being ad justable laterally of the feed table.- The front ends of the'tongues15 extend beyond the lip plate 13 and come into'close proximity with the cylinder surface. I

In suitable members such as that indi-' cated at 16 is mounted a cross bar 17 upon which are secured a pair of front guides 18,

guide consists of a casting 19 having a tubular portion 20. in which is slidably mounted a stem 21, a spring 22 being interposed between the stem and the casting, and tending to press the stem 21' outwardly. Passing longitudinally through the casting 19 and threaded into the stem 21 is a screw 23 hav ing at its outer end a vknurled head 24 with which engages a 'detent spring 25 mounted on top of thecastingy To the front end of the stem 21 is secured a gauge plate 26 having ears 27 extending downwardly therefrom and each-side of the latter, as'shown in Fig. 4,

one onlyof which is shown. Each front head tOhaving thereby preventing the edge of the sheet from entering beneath the gauge plate. A fine adjustment of the gauge plate towards and from the feed table can be effected by rotating the knurled head 24 manually, such head being retained in its adjusted posltlon'by means of the detent spring 25. Bymanipulating the knurled heads 24 of the two front guides, and by adjusting a side register deviceon the feed table (of which many kinds 7 are well known in the art), the position of the sheet on the cylinder can be determined with great accuracy. The sheet is, ofcourse, fed against the gauge plates 26 of the front guides, so that its front edge is exposed, eX- cept for those portions which lie on the tongues 15. From this position it is withdrawn by the grippers on thecylinder 11, the front guides being made to rise, in a well known manner, to permit this.

, For detecting the presence or absence of a sheet at the gauge plates 26 of the front guides, each gauge'plate has pivoted thereto a detecting member 28, which includes a pair of arms 29 connected by a pin 30'which is pivotally mounted in ears31 extending rearwardly from thegauge plate. The arms 29 are connected by a frontportion 32 having a downwardly extending leaf 33 and an upwardly extending lafBP. .The downwardly extending'leaf 33 is adapted to enter a slot 35 formed in the associated tongue 15 and the arms 29 are provided with a counterweight 36which tends to swing the whole detecting member v28 into a position. in which the leaf 33 stands in the slot 35 in a position in advance of the gauge plate 26, as indicatedinFig.5. I is The stem 21 is made hollow and contains a plunger 37which is normally pressed out: wardiy, by means ofa spring 38 disposed between said plunger and the end of the screw- 23, the possible outward movement of the plunger being limited by a-screw 39. The plunger protrudes from jthefront endof the stem 21 and is formed at that point with a an annular groove 41 formed therein; The positionand dimensions of the parts are suchthat when the detector memberis in itsnormal position, shown in Fig. 5, its upper leaf 34'Wlll be disposed in the groove 41, and willprevent movement of the plunger inwardly with respect to the stem 21.. When, however, a sheet: is fed correctly, so that its edge comes into registering engage ment with the gauge plate 26, such edge will push the lower leaf 33 forward, rocking. the detector member about its pivot; and-cause such lower leaf to enter a slot42formedfor the purpose in the gauge plate 26. ,Such

rocking movement of the detector member will cause its upper leaf 3t'to swing forward into a position in which it no longer enters the rooveltlfofthe plunger 37." In these circumstances, the plunger 37, is free to move inwardly with respect to the sleeve 21. It is the fact of whether or not the plunger 37 is free for inward movement that controls whether the press shall continue to print, or

whether it shall be stopped or its impression ance to the feeding of the sheet and yet resist any tendency of the sheetto bounce back from the gauge plates 26 of thefront guides. They are so adjusted as to make alignment with the slots 35 ofthe tongues 15; so as to stiffen the front edge of the sheet, and iron it out, just at that point where it is required to operate upon the leaves 33 of the detector members. This, in connection with the fact that the leaves 33 extend into the slots 35, thereby precluding any change of the edge of the sheet passing beneath the leaves, renders the device entirely certain in its operation, regardless of thinness of the sheet or of any tendency of the latter to curl either downwardly or upwardly.

- Extending across the feed table 12 is a rock shaft 46 operated upon by a torsion spring 46a, or some other means tending to rock the same in a clockwise direction, when viewed as inFig. 2. Such rockshaft has mounted for lateral adjustment thereon a pair of tappet levers 47, one for each of the front guides. These tappet levers have engaging portions 48 which, when the parts are adjusted, stand opposite the heads of the plungers 3' 7. At its outer end, the shaft 46 is provided with a lever49 having an abutment portion 50 which lies above a vertically reciprocablerod 51. The details of the mechanism actuating, and actuatedby, the rod 51 are not of interest here. The rod is reciprocate'd once for each cycle of the press, thereby, by its engagement with the abutment portion 50, causing the shaft 46 to rock against the action of its spring 46a, and then return. The mechanism, further, is such that when, at a time when a sheet should bepresented tothefront guides, the spring 46adoes not, through the lever 49, exert its pressure downwardlyupon the rod 51, the press will either be stopped, or the impression of the press will be thrown off, or both, accord-ingto how it is desired to constitute the mechanism, When,- however. at that period, pressureofthe'spring 4600 is exerted downwardly on the rod 51, the press will continue to print. Y 1

It will be seen that when the sheets are fed correctly, so as to makeregistering engages ment with the gauge plates'26 of thefront guides, the detector members will' be pushed leaves 37. In these circumstances, whenthe rod 51 descends and the sprlng 46a causes the en- T forward so that their upper leaves 34 pass out of the slots 41 of the plungers 37. Under these conditions, when the rod 51 descends, the engaging portions 48 of the tappet levers 4'? can push the plungers inwardly with respect to the stems 21, and accordingly the shaft 46 can rock clockwise under the action of its spring 46a, thelatter exerting a down-- ward thrust upon the rod 51. Under these conditions, the press will continue to print;

lVhen, however, a sheet does not reach the gauge plates 26 of the front guides, the detector members 28 will remain in the position shown in Fig. 5, in which the upper 34 lie in the grooves 41 of the plungers gaging portions 48 of the tappet levers 47 to push against the heads 40 of the plungers 87, the latter are prevented, by the upper leaves 34,from moving inwarclly,fand the shaft 46 is thereby held against further rock ing movement; Thus the spring 46a cannot exert any downward pressure upon the rod 51. Under these conditions, the press will either be stopped, or itsimpression will be thrown off, or both, according to how the,

mechanism is constituted. There are two of the front guides and associateddetec'ting members, either of which functions separately. Therefore if a sheet should be fed properly against the gauge plate 26 of one front guide, but not against the other, the press stoppage, or impression throw off, or both,

will occur, as will also take place if a sheet having a portion of its front edge torn away should present itself. Iclaim: l The combination with a feed table having a sheet supporting member formed with a slot therein, and a front guide movable into and out of operative position and having. a gauge cooperating with said member, of a rock shaft mounted on said table, tripping. mechanism associated with said rock shaft 1 to be operated when said shaft is not rocked,

I an abutment member on said rock shaft, a

plunger reciprocably mounted on said front guide for bodily movement therewith, said plunger being disposed for engagement by said abutment member, whereby when said plunger 15 locked agamstmovement, said rock shaft is prevented from being rocked,

said plunger having a groove in the end thereof and a detecting member carriedzby said front guide and havinga portion adapted to enter said slot, whereby said detecting member is moved from one position to another when a sheet is fed against said gauge,

said detecting member having a portion adapted to enter said groove, thereby to lock said plunger against movement, when said detecting member is in one of its positions.

In testimony whereof, I sign my name. ALFRED WILLIAM BARRETT. 

